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This is a blog about paleontology (the study of the history of life on Earth through the fossil record) with an emphasis on vertebrate paleontology, the study of extinct vertebrates (animals with backbones). The methodology and findings of paleontology will be discussed, as well as related issues such as evolutionary theory. The blogger is a vertebrate paleontologist specializing in the Triassic Period, the Beginning of the Age of Dinosaurs.

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

In the last two blogs (click here for Part I and Part II), we've been talking about ways of determining the relative ages of sedimentary rocks and fossils (e.g. species A lived some time before species B), without determining their exact numeric ages (in thousands, millions, or billions of years). This is referred to as "relative age dating." If we start applying numeric ages, we are talking about "absolute age dating." The main method by which this is done is called radioisotopic dating. Explaining how radioisotopic dating works is going to require that I hop around a bit between subjects, but it will all come together in the end.

Just to give a little basic physics recap, an atom is made up of three types of particles: protons, neutrons, and electrons. The number of protons determines the type of atom (and element); for example, an atom of potassium (K) always has 19 protons, which is its "atomic number". The number of neutrons only changes the mass of the atom; atoms with the same number of protons but different numbers of neutrons . . . More